JPH0699371A - Control method utilizing acceleration change of industrial robot - Google Patents

Abstract

PURPOSE:To provide a control method for an industrial robot whereby abnormality of a driven robot can be quickly detected by a very small delay of action further with high accuracy. CONSTITUTION:A method contains a process of detecting a position of a robot by a predetermined period, process of calculating a speed of the robot by the detected robot latest position and the detected position just before and a process of calculating acceleration of the robot by the calculated robot latest speed and the calculated speed just before. The method contains a process for obtaining a permissible position deviation corresponding to the calculated acceleration, process for obtaining the latest position deviation of the robot by its latest position and target position and a process for generating a different command to the robot in accordance with whether the latest position deviation is within the permissible position deviation or not.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling an industrial robot. More specifically, the present invention relates to a method for controlling an industrial robot that can quickly detect an abnormality in the robot.

[0002]

2. Description of the Related Art Conventionally, in an industrial robot, the position of the robot is controlled by feedback control. When this feedback control is used, an operation delay of about 0.1 second occurs with respect to the command value due to its control characteristics. Therefore, the target position and the current position of the robot have a position deviation determined by the product of the operation delay and the moving speed of the robot. Due to its nature, this positional deviation increases in proportion to the speed of the robot. If the position deviation becomes too large, the robot may lose its mounting accuracy, or the robot may move out of the specified trajectory and come into contact with an object on the side of the track, resulting in damage to the robot or the object. There is also a nature. In order to avoid such a situation, measures are taken such as monitoring the position deviation and stopping the robot when the value exceeds a predetermined value (limit value). At present, the limit value is set to a value calculated based on the maximum speed and motion delay of the robot, or a value calculated based on the speed and motion delay of the robot (FIG. 5). reference).

However, in recent servo technology,
By utilizing feedforward, dynamic feedforward, modern control theory, etc., it has become possible to drive a robot with a very small operation delay (delay of about 4 milliseconds) and with high accuracy. Therefore, monitoring the position deviation of the robot using the conventional limit value causes a problem that if the limit value is too loose and an abnormality occurs in the robot, the abnormality cannot be detected quickly. Is coming. Further, if the speed is steady and low, the position deviation is small, but when the direction of the speed changes, such as when changing from forward to backward, the position deviation becomes large despite the small speed. Therefore, it is difficult to set a sufficiently small limit value at low speed.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art, and is an industry capable of quickly detecting an abnormality of a robot which is driven with a very small operation delay and with high accuracy. It is an object of the present invention to provide a control method for a mobile robot.

[0005]

The inventors of the present invention, as a result of diligent research on the above-mentioned problems, have found that when the robot is accelerated or decelerated, it causes a larger motion delay than usual, and this acceleration It has been found that the above-mentioned problems can be solved by monitoring the position deviation of the robot on the basis of the motion delay caused by the change of The present invention has been made based on such findings.

That is, the industrial robot control method of the present invention calculates the speed of the robot based on the procedure of detecting the position of the robot at a predetermined cycle, and the latest position of the robot detected by the above and the detected position immediately before it. Procedure, a procedure for calculating the acceleration of the robot by the latest speed of the robot calculated above and the calculated speed immediately before it, a step of obtaining an allowable position deviation corresponding to the calculated acceleration, and a Depending on the position and the target position, the procedure for obtaining the latest position deviation of the robot, and whether the latest position deviation is within the allowable position deviation,
It is characterized by including a procedure for changing instructions to the robot.

In the industrial robot control method of the present invention, if the latest position deviation is within the allowable position deviation, an instruction to continue the work being executed is given, and the latest position deviation is determined to be the allowable position deviation. If it is out of deviation, it is preferable to instruct to stop the robot.

[0008]

In the present invention, since the industrial robot is controlled by the above procedure, the limit value in the steady state where the acceleration does not change can be made very small. Therefore, it is possible to quickly detect the position deviation due to overload or the like.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described based on embodiments with reference to the accompanying drawings, but the present invention is not limited to such embodiments.

FIG. 1 is a schematic diagram of a robot using the control method of the present invention, FIGS. 2 to 3 are flowcharts of the control method of the present invention, and FIG. 4 is a graph showing the relationship between the limit value and the acceleration in the present invention. . In FIG. 1, 1 is an input device, 2 is a robot controller, 3 is a robot body, and 4 is a sensor.

A robot to which the present invention is applied, the outline of which is shown in FIG. 1, has an input device 1, a robot controller 2, a robot body 3 and a sensor 4 as main constituent elements.

The robot controller 2 has an input / output interface, a RAM, a ROM, a clock, and a servo control section. A program for executing the procedure shown in the flowcharts of FIGS. 2 to 3 is stored in this ROM. The description of the specific configurations of the input / output interface, the RAM, the ROM, the clock, and the servo control unit used in the robot controller 2 will be omitted, but those conventionally used in this type of robot controller are preferably used. In addition to the programs described above, the ROM also stores other programs necessary for controlling the robot.

Next, one embodiment of the control method of the present invention will be described with reference to the flow charts shown in FIGS.

Step 1: The robot body 3 is activated.

Step 2: The initial position of the robot hand 3 is stored in the RAM.

Step 3: The robot body 3 is made to perform a predetermined work.

Step 4: The sensor 4 detects the position of the robot hand. The position of this hand may be calculated based on the data that the robot controller 2 itself has.

Step 5: R of the robot controller 2
The position of the robot hand is stored in AM.

Step 6: The movement amount of the hand is calculated from the difference between the position of the robot hand input last time and the position of the robot hand input this time.

Step 7: The moving amount is divided by the required time to calculate the speed of the robot hand, and the value is stored in the RAM.

Step 8: Calculate the speed difference between the speed of the robot hand calculated last time and the speed of the robot hand calculated this time.

Step 9: The speed difference is divided by the required time to calculate the acceleration of the robot hand, and the calculated value is stored in the RAM.
To memorize.

Step 10: Calculate a limit value of the position deviation according to the acceleration. The relationship between this limit value and acceleration is
For example, as shown in FIG. 4, it is provided in advance in the ROM in the form of a linear function.

Step 11: The position deviation is calculated by obtaining the difference between the position of the robot hand detected in step 4 and the target position.

Step 12: Compare the position deviation with a limit value.

Step 13: If the positional deviation does not exceed the limit value, the robot body 3 is instructed to continue the work being executed, and then the process returns to step 4.

Step 14: If the position deviation exceeds the limit value, an instruction to stop the robot body 3 is issued.

Although the method for monitoring the position deviation of the robot hand has been described above based on the embodiment, the present invention is not limited to this embodiment. For example, the detection target may be a joint angle position of each axis of the robot instead of the robot hand position. That is, the control method of the present invention can be applied in the same manner by providing a limit value of the angular deviation for the angular acceleration of each axis.

[0029]

As described above, according to the control method of the present invention, it is possible to quickly detect an abnormality in the position deviation of a robot controlled by a very small motion delay of about 4 milliseconds. it can. Further, since the limit value of the position deviation can be reduced to about 1/10 of the conventional value, the positioning accuracy can be improved.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a robot using a control method of the present invention.

FIG. 2 is a part of a flowchart of a control method of the present invention.

FIG. 3 is a part of a flowchart of a control method of the present invention.

FIG. 4 is a graph showing a relationship between a limit value and acceleration according to the present invention.

FIG. 5 is a graph showing a conventional relationship between a limit value and speed.

[Explanation of symbols]

 1 Input device 2 Robot controller 3 Robot body 4 Sensor

Claims (3)

[Claims] 1. A procedure for detecting the position of a robot at a predetermined cycle, a procedure for calculating the speed of the robot based on the latest position of the robot detected by the above and the detected position immediately before it, and a procedure for calculating the speed of the robot calculated by the above. The procedure of calculating the acceleration of the robot from the latest speed and the calculated speed immediately before it, the procedure of obtaining the allowable position deviation corresponding to the calculated acceleration, and the latest position of the robot and the target position Control of the industrial robot characterized by including a procedure for obtaining the position deviation of the robot and a procedure for changing the instruction to the robot depending on whether or not the latest position deviation is within the allowable position deviation. Method. 2. The control method for an industrial robot according to claim 1, wherein when the latest position deviation is within the allowable position deviation, an instruction to continue the work being executed is issued. 3. The method for controlling an industrial robot according to claim 1, wherein when the latest position deviation is outside the allowable position deviation, a stop of the robot is instructed.